A sit down and stand up walker for assisting a user during walking and when not walking in a standing, partially standing or sitting positions with partial or full weight bearing support and with means to change from standing, partially standing to sitting positions with partial weight bearing support to a fixed elevation with full weight bearing support in any varied or repeated sequence. The partial or full weight bearing means supports a seat assembly which includes a seat and front body support with adjustable positioning to provide pelvic stability. The angle of the seat assembly relative to a flat ground surface is maintained at any elevation of the seat assembly between a standing and sitting position. The weight bearing means is responsive to the variable force supplied by the user as the user walks, stands or sits allowing the seat assembly to move up or down. The weight bearing means in a preferred embodiment is an enclosed gas spring cylinder with piston rod that can be locked at differing elevations or released to respond to a user's body force as the user walks, stands or sits. The walker is intended to be moved without the user's hands holding onto the frame thereby promoting a normal gait and posture. The walker enables the user to expend less energy as the body's center of gravity with partial or full weight bearing support rises and falls with each stride. The walker facilitates transfers from a sitting to standing positions and vice versa by the user independently without the intervention of caregivers.